National Landslide Preparedness Act This bill: (1) directs the U.S. Geological Survey (USGS) to establish a National Landslide Hazards Reduction Program to identify and understand landslide hazards and risks, reduce losses from landslides, protect communities at risk of landslide hazards, and help improve communication and emergency preparedness; and (2) establishes the Interagency Coordinating Committee on Landslide Hazards to oversee the program. The USGS shall: develop and publish a national strategy for landslide hazards and risk reduction in the United States; develop and maintain a publicly accessible national landslide hazard and risk inventory database; disseminate landslide planning and risk reduction materials; expand the early warning system for flash floods and debris flow; establish emergency response procedures for the rapid deployment of federal scientists, equipment, and services to areas impacted by a significant landslide event; support emergency response efforts and improve the safety of emergency responders establish the Advisory Committee on Landslides; and support the identification, mapping, research, and monitoring of subsidence and groundwater resource accounting. The USGS may provide competitive grants to state, local, and tribal governments to research, map, assess, and collect data on landslide hazards. The National Science Foundation shall ensure that landslide research grants are provided on a competitive basis to advance the goals and priorities of the national strategy. The USGS shall establish the 3D Elevation Program and the 3D Elevation Federal Interagency Coordinating Committee. The program shall: provide 3D elevation data coverage for the United States; coordinate and facilitate the collection, dissemination, and use of 3D elevation data among federal agencies and non-federal entities; produce standard, publicly accessible 3D elevation data products for the United States; and promote the collection, dissemination, and use of 3D elevation data among federal, state, local, and tribal governments, communities, institutions of higher education, and the private sector. The USGS may make grants and enter into cooperative agreements to facilitate the improvement of nationwide coverage of 3D elevation data.